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<div class="subTitle">org.apache.commons.lang3.concurrent</div>
<h2 title="Class LazyInitializer" class="title">Class LazyInitializer&lt;T&gt;</h2>
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<li>org.apache.commons.lang3.concurrent.LazyInitializer&lt;T&gt;</li>
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<dl><dt><span class="strong">Type Parameters:</span></dt><dd><code>T</code> - the type of the object managed by this initializer class</dd></dl>
<dl>
<dt>All Implemented Interfaces:</dt>
<dd><a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentInitializer.html" title="interface in org.apache.commons.lang3.concurrent">ConcurrentInitializer</a>&lt;T&gt;</dd>
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<pre>public abstract class <span class="strong">LazyInitializer&lt;T&gt;</span>
extends <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a>
implements <a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentInitializer.html" title="interface in org.apache.commons.lang3.concurrent">ConcurrentInitializer</a>&lt;T&gt;</pre>
<div class="block"><p>
 This class provides a generic implementation of the lazy initialization
 pattern.
 </p>
 <p>
 Sometimes an application has to deal with an object only under certain
 circumstances, e.g. when the user selects a specific menu item or if a
 special event is received. If the creation of the object is costly or the
 consumption of memory or other system resources is significant, it may make
 sense to defer the creation of this object until it is really needed. This is
 a use case for the lazy initialization pattern.
 </p>
 <p>
 This abstract base class provides an implementation of the double-check idiom
 for an instance field as discussed in Joshua Bloch's "Effective Java", 2nd
 edition, item 71. The class already implements all necessary synchronization.
 A concrete subclass has to implement the <code>initialize()</code> method, which
 actually creates the wrapped data object.
 </p>
 <p>
 As an usage example consider that we have a class <code>ComplexObject</code> whose
 instantiation is a complex operation. In order to apply lazy initialization
 to this class, a subclass of <code>LazyInitializer</code> has to be created:
 </p>

 <pre>
 public class ComplexObjectInitializer extends LazyInitializer&lt;ComplexObject&gt; {
     &#064;Override
     protected ComplexObject initialize() {
         return new ComplexObject();
     }
 }
 </pre>

 <p>
 Access to the data object is provided through the <code>get()</code> method. So,
 code that wants to obtain the <code>ComplexObject</code> instance would simply
 look like this:
 </p>

 <pre>
 // Create an instance of the lazy initializer
 ComplexObjectInitializer initializer = new ComplexObjectInitializer();
 ...
 // When the object is actually needed:
 ComplexObject cobj = initializer.get();
 </pre>

 <p>
 If multiple threads call the <code>get()</code> method when the object has not yet
 been created, they are blocked until initialization completes. The algorithm
 guarantees that only a single instance of the wrapped object class is
 created, which is passed to all callers. Once initialized, calls to the
 <code>get()</code> method are pretty fast because no synchronization is needed
 (only an access to a <b>volatile</b> member field).
 </p></div>
<dl><dt><span class="strong">Since:</span></dt>
  <dd>3.0</dd>
<dt><span class="strong">Version:</span></dt>
  <dd>$Id: LazyInitializer.java 1583482 2014-03-31 22:54:57Z niallp $</dd></dl>
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<td class="colOne"><code><strong><a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html#LazyInitializer()">LazyInitializer</a></strong>()</code>&nbsp;</td>
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<td class="colFirst"><code><a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html" title="type parameter in LazyInitializer">T</a></code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html#get()">get</a></strong>()</code>
<div class="block">Returns the object wrapped by this instance.</div>
</td>
</tr>
<tr class="rowColor">
<td class="colFirst"><code>protected abstract <a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html" title="type parameter in LazyInitializer">T</a></code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html#initialize()">initialize</a></strong>()</code>
<div class="block">Creates and initializes the object managed by this <code>LazyInitializer</code>.</div>
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<h3>Methods inherited from class&nbsp;java.lang.<a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a></h3>
<code><a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#clone()" title="class or interface in java.lang">clone</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#equals(java.lang.Object)" title="class or interface in java.lang">equals</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#finalize()" title="class or interface in java.lang">finalize</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#getClass()" title="class or interface in java.lang">getClass</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#hashCode()" title="class or interface in java.lang">hashCode</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#notify()" title="class or interface in java.lang">notify</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#notifyAll()" title="class or interface in java.lang">notifyAll</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#toString()" title="class or interface in java.lang">toString</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#wait()" title="class or interface in java.lang">wait</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#wait(long)" title="class or interface in java.lang">wait</a>, <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true#wait(long, int)" title="class or interface in java.lang">wait</a></code></li>
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<h4>LazyInitializer</h4>
<pre>public&nbsp;LazyInitializer()</pre>
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<h4>get</h4>
<pre>public&nbsp;<a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html" title="type parameter in LazyInitializer">T</a>&nbsp;get()
      throws <a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentException.html" title="class in org.apache.commons.lang3.concurrent">ConcurrentException</a></pre>
<div class="block">Returns the object wrapped by this instance. On first access the object
 is created. After that it is cached and can be accessed pretty fast.</div>
<dl>
<dt><strong>Specified by:</strong></dt>
<dd><code><a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentInitializer.html#get()">get</a></code>&nbsp;in interface&nbsp;<code><a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentInitializer.html" title="interface in org.apache.commons.lang3.concurrent">ConcurrentInitializer</a>&lt;<a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html" title="type parameter in LazyInitializer">T</a>&gt;</code></dd>
<dt><span class="strong">Returns:</span></dt><dd>the object initialized by this <code>LazyInitializer</code></dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentException.html" title="class in org.apache.commons.lang3.concurrent">ConcurrentException</a></code> - if an error occurred during initialization of
 the object</dd></dl>
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<h4>initialize</h4>
<pre>protected abstract&nbsp;<a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html" title="type parameter in LazyInitializer">T</a>&nbsp;initialize()
                         throws <a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentException.html" title="class in org.apache.commons.lang3.concurrent">ConcurrentException</a></pre>
<div class="block">Creates and initializes the object managed by this <code>LazyInitializer</code>. This method is called by <a href="../../../../../org/apache/commons/lang3/concurrent/LazyInitializer.html#get()"><code>get()</code></a> when the object
 is accessed for the first time. An implementation can focus on the
 creation of the object. No synchronization is needed, as this is already
 handled by <code>get()</code>.</div>
<dl><dt><span class="strong">Returns:</span></dt><dd>the managed data object</dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../../../org/apache/commons/lang3/concurrent/ConcurrentException.html" title="class in org.apache.commons.lang3.concurrent">ConcurrentException</a></code> - if an error occurs during object creation</dd></dl>
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